Many electronic applications require some form of electrical isolation in order to protect circuits from large voltage spikes, as for example, may be encountered in industrial controls. Electrical isolation avoids ground loops that significantly increase system noise, and isolation also serves to link signals between circuits having large offsets in DC voltage levels.
Heretofore, such isolation has often been done by using opto-couplers, in which, typically light-emitting diodes and optical sensors are employed. Opto-couplers require hybrid fabrication techniques, and are therefore more expensive than pure silicon integrated circuits.
Thus, it is an object of the present invention to provide electrical isolation of connected circuits without having to employ opto-couplers.
Another object is to provide electrical isolation by means of a magnetic coupling system.
Another object of the invention is to provide a more versatile and, at the same time, less expensive technology in the field of electrical isolation couplers.
Another object is to avoid hybrid technologies and to construct an isolator using only silicon technology.
Other objects are to eliminate the influence of stray magnetic fields in a magnetic coupler-isolator, to provide for a self-calibrating magnetometer, to improve magnetometer sensitivity, and to reduce the sensitivity to temperature.
A further object is to reduce or eliminate signal offsets in carrier-domain-magnetometers, which are caused by asymmetry in the magnetometer. Offsets have been a problem in carrier-domain-magnetometers. (An input offset is the input required for zero output. Offsets in carrier-domain-magnetometers have been mainly due to spatial misalignments between the different layers in the device. The problem of offsets is complicated by the difficulty of aligning the buried layer in bipolar integrated-circuit technologies with the rest of the masks.
Still other objects and advantages of the invention will appear from the following description.